Missing sapi signing buttons

[0xKheops]

When signing with sapi (ex: staking) there is a dedicated button component for each account type (ledger, keypair, qr...)
If account is not a keypair, ledger or qr, it throws an error which oopsies the form

TODO :

• Handle all account types that are able to sign (add signet and any other missing ones)
• Display a disabled sign button instead of throwing an error, if the account type isnt supported yet